JPS60254731A - Manufacture of semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a semiconductor device having flat surface of oxide film by executing dry etching after eliminating perfectly the alumina layer at the aluminum surface by the wet etching. CONSTITUTION:Aluminum 9 is vacuum deposited on an oxide film 7 formed on a silicon substrate 6 and an aperture 8 thereof and an alumina layer 10 is formed on aluminum 9 by natural oxidation or anode oxidation. Moreover, the alumina layer 10 is coated with the resist 11 only at the required area as the electrode of semiconductor device. The section of the alumina layer 10, where is not coated with resist 11 is eliminated by the wet etching utilizing acetic acid and ammonium fluoride. In this case, since the alumina layer 10 is perfectly removed, the surface of aluminum 9 can also be removed in such a thickness as 1,000-2,000Angstrom by the wet etching using organic alkali system or phosphoric acid. Moreover, aluminum 9 at the area not coated with resist 11 is removed by dry etching utilizing reactive ion etching and the resist 11 is finally removed.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Technical Field of the Invention The present invention relates to patterning of aluminum electrodes, and particularly to patterning of aluminum electrodes formed on oxide films by dry etching.

The present invention relates to a method of manufacturing a semiconductor device that does not damage an oxide film.

(2) Background of the invention For manufacturing semiconductor devices such as planar transistors.

Etching is repeatedly performed to process aluminum electrodes and remove photoresist. Generally speaking, there are two types of etching: wet etching, which uses a liquid to remove unnecessary aluminum and photoresist, and dry etching, which uses plasma to dissolve unnecessary aluminum and photoresist in a gas such as carbon fluoride.

Dry etching is particularly used at present because it does not require manual control of the purity of chemicals and can easily replace two work steps with machine work.

(3) Prior art and problems FIG. 1 +al to tc) shows a manufacturing process in which an aluminum electrode is processed by dry isoetching in a semiconductor device.

First, as shown in the same figure (al), a silicon (St) substrate 1
Aluminum (Aβ) 3 is deposited on the silicon oxide (SiO2) oxide film 2 formed above and the opening 2a of the oxide film 2, and an alumina layer 4 is formed on the aluminum 3 by natural oxidation or anodic oxidation. A resist 5 is applied onto the alumina layer 4 only on the portions required as electrodes, and the aluminum electrodes are patterned. Next, as shown in FIG.
is removed by dry enching. In addition, the same figure tel.
In the process shown in Figure 3, the aluminum 3 in the areas where the resist is not coated is removed by dry etching.

Finally, the resist 5 is removed.

Through the process described above, electrode patterning of aluminum 3 was performed on the oxide film 2 and the openings of the oxide film 2.

However, since reactive ion etching (RIE) is used as dry etching at this time, the alumina layer 4 formed on the surface of the aluminum 3 is
As shown in the figure, etching with uneven steps is performed.

Furthermore, this step is created when etching aluminum 3.
The oxide film 2, which is an insulating layer, is also affected, and the surface of the oxide film 2 becomes uneven, as shown in FIG. 2(C). In other words, the oxide film 2 before dry etching has a thickness of about 4000 mm.
After dry etching, the thickness of the convex portions is approximately 3000 mm and the thickness of the concave portions is approximately 1000 mm. This oxide film 2 is an insulating layer of a semiconductor device, and when unevenness occurs in the oxide film 2, insulation failure occurs in the depressions, which may cause a short circuit.

Furthermore, in order to prevent the recesses formed in the oxide film 2 from reaching the silicon substrate 1, the dry etching time of the aluminum 3 must be carefully controlled.

(4) Purpose of the Invention In view of the above-mentioned conventional drawbacks, the present invention provides a method to completely remove the alumina layer on the aluminum surface by wet etching, and then perform dry etching to prevent unevenness from occurring on the surface of the oxide film. The purpose of the present invention is to provide a method for manufacturing a semiconductor device.

(5) Summary of the Invention The above object is achieved by the following steps: (1) According to the present invention, an insulating film is formed on the surface of a semiconductor substrate, an aluminum layer is formed on the insulating film, and a predetermined pattern film is formed on the aluminum layer. A method for manufacturing a semiconductor device comprising the steps of: completely removing the alumina layer on the surface of the aluminum layer by wet etching using the patterned film as a mask; and removing the aluminum layer by dry etching using the patterned film as a mask. This is achieved by providing

(6) Embodiments of the Invention The following two embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 2, an oxide film 7 formed on a silicon substrate 6
Then, aluminum 9 is deposited to a thickness of, for example, 1 μm in the opening 8 of the oxide film 7 by the process shown in +a) in the figure, and an alumina layer of 1° is formed on the aluminum 9 by natural oxidation or anodic oxidation. Furthermore, a resist 11 is applied onto the alumina layer 10 only in the portions required as electrodes of the semiconductor device. Next, in the process shown in Tbl in the same figure, the resist 1 is etched by wet etching using acetic acid and ammonium fluoride.
The portions of the alumina layer 10 to which 1 is not coated are removed.

In order to completely remove the alumina layer 10 at this time.

The surface of aluminum 9 can also be etched to a thickness of 1,000 to 20 mm by wet etching using organic alkali or phosphoric acid.
About 00 people will be removed. Further, in the process shown in the same figure (C1), the portions of the aluminum 9 on which the resist 11 is not applied are removed by dry etching using reactive ion etching, and finally the resist 11 is removed.

Through the process described above, an electrode made of aluminum 9 can be provided on the silicon substrate 6.

When the alumina layer 10 on the surface of the aluminum 9 is first removed by wet etching in this way, the unevenness that conventionally occurs when the alumina layer 10 is removed by dry etching does not occur.

Furthermore, unevenness does not occur in the alumina layer 10.

Even if dry etching is then performed to remove all of the aluminum 9, the surface of the oxide film 7 will not become uneven. Therefore, the surface of the oxide film 7 is flat, the thickness of the oxide film 7 is about 3000 Å, and the thickness is constant at each part of the oxide film 7. Therefore, the aluminum electrode 9 and the silicon 6 are reliably insulated from the external conductive material.

The present invention is not limited to the above embodiments, and when removing the aluminum 9 and the alumina layer 10 by wet etching, the thickness of the aluminum 9 to be removed is 1000 ~
The removal is not limited to 2,000 people, but can be performed even if other thicknesses are removed.

(7) Effects of the Invention As described in detail above, according to the present invention, since no unevenness occurs in the oxide film which is the insulating film of the semiconductor, it is possible to reliably insulate the semiconductor device.

In addition, since the oxide film 7 does not have any unevenness, the aluminum 9
Etching time for dry etching can be easily managed.

[Brief explanation of drawings]

1+al~(C1 is a manufacturing process diagram of a conventional semiconductor device. FIGS. 2+a)~lc) are manufacturing process diagrams of a semiconductor device of the present invention. 6...Silicon, 7...Oxide film. 9... Aluminum, 10... Alumina layer, 1
1...Resist Figure 1 (b) (C) Figure 2 (b) (C)

Claims (2)

[Claims] (1) A process of forming an insulating film on the surface of a semiconductor substrate and forming an aluminum layer on the insulating film, forming a predetermined pattern film on the aluminum layer, and using the pattern film as a mask to form an aluminum layer on the aluminum surface. A method for manufacturing a semiconductor device comprising the steps of completely removing an alumina layer by wet etching, and removing the aluminum layer by dry etching using the patterned film as a mask. (2) The method of manufacturing a semiconductor device according to claim 1, wherein the wet etching step includes etching the extreme surface layer of the aluminum layer after removing the alumina layer.